Numbers are omnipresent in our society, and dealing with numbers (e.g. in a supermarket or at school) is a key cognitive competence that has a crucial impact on our socio-economic status and well-being. The aim of this project is to explore basic cognitive and neuronal aspects of numerical cognition.

How do humans deal with abstract information such as numbers? In cognitive psychology, it is assumed that the processing of abstract contents is supported by strategies that are based on more concrete, directly graspable domains. Previous research suggests that numbers are cognitively represented in terms of a spatially oriented mental number line (from left to right in ascending order for Western cultures) – and that this mental number line is implicitly activated when processing numbers. In the present project, we study the role of this mental number line for mental arithmetic. To this end, for instance, we measure and manipulate participants’ eye movements when they perform mental arithmetic. Moreover, the neural representation of numbers and arithmetic is far from clear. By means of brain stimulation techniques, we explore the role of specific brain areas for mental arithmetic and assess whether mental arithmetic can be enhanced by brain stimulation. In addition to basic knowledge, the insights from this project will be useful for a better understanding of the relationship between brain damage and number processing, and also for advancing interventions aimed at improving arithmetic competence.


  • Hartmann, M., Martarelli, C. S., & Sommer, N. R. (2021). Early is left and up: Saccadic responses reveal horizontal and vertical spatial associations of serial order in working memory. Cognition217, 104908. 
  • Hartmann et al., (in press). Anodal High-definition Transcranial Direct Current Stimulation over the Posterior Parietal Cortex Modulates Approximate Mental Arithmetic. Journal of Cognitive Neuroscience
  • Hartmann, et al. (2019). Sharing a mental number line across individuals? The role of body position and empathy in joint numerical cognition. Quarterly Journal of Experimental Psychology, 72, 1732-1740


Prof. Dr. Matthias Maalouli-Hartmann
Prof. Dr. Matthias Maalouli-Hartmann Associate professor
René Müri
René Müri Professor, Neurology, University Hospital Bern
Professor, Institute of Psychology, University of Bern
Nils Sommer
Nils Sommer Research assistant